Users of synchronized online content management systems, such as Dropbox from Dropbox Inc. of San Francisco, Calif., may store hundreds, or even thousands, of content items in their content management system user accounts. These users frequently attach files and other content items within an email client and other applications by navigating a file chooser invoked through the email composition window or by dragging content to the email composition window. If the email client is not designed to access content in the content management system directly, the user may have to locate and download the desired content item from the content management system onto local storage first, and then upload the content through the email client. This can be inconvenient and cumbersome for users especially if the desired content item is tucked away in an obscure corner of a complex hierarchical folder structure inside the content management system. Inserting a share link to the content item in the email can be also prone to errors. While trying to obtain the link from the content management system and type it into the email composition window, the user may introduce typographical errors into the link and render the link inaccessible.
Additionally, when another user receives the email with the attachment, the recipient generally has to download the attachment before she is able to access the attached content. Although some email applications offer a functionality to view a preview of certain types of content inline, these previews are limited to files that are attached to the email and no previews are generated for links to content stored in an online content management system. Moreover, usually it takes several steps to add an attachment from a content management system account or save an attachment to the user account with the content management system.